/*
 * jdpostct.c
 *
 * Copyright (C) 1994-1995, Thomas G. Lane.
 * This file is part of the Independent JPEG Group's software.
 * For conditions of distribution and use, see the accompanying README file.
 *
 * This file contains the decompression postprocessing controller.
 * This controller manages the upsampling, color conversion, and color
 * quantization/reduction steps; specifically, it controls the buffering
 * between upsample/color conversion and color quantization/reduction.
 *
 * If no color quantization/reduction is required, then this module has no
 * work to do, and it just hands off to the upsample/color conversion code.
 * An integrated upsample/convert/quantize process would replace this module
 * entirely.
 */

#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"


/* Private buffer controller object */

typedef struct {
    struct jpeg_d_post_controller pub;/* public fields */

    /* Color quantization source buffer: this holds output data from
     * the upsample/color conversion step to be passed to the quantizer.
     * For two-pass color quantization, we need a full-image buffer;
     * for one-pass operation, a strip buffer is sufficient.
     */
    jvirt_sarray_ptr whole_image;/* virtual array, or NULL if one-pass */
    JSAMPARRAY       buffer;/* strip buffer, or current strip of virtual */
    JDIMENSION       strip_height; /* buffer size in rows */
    /* for two-pass mode only: */
    JDIMENSION starting_row;/* row # of first row in current strip */
    JDIMENSION next_row;    /* index of next row to fill/empty in strip */
} my_post_controller;

typedef my_post_controller * my_post_ptr;


/* Forward declarations */
METHODDEF void post_process_1pass
JPP( ( j_decompress_ptr cinfo,
       JSAMPIMAGE input_buf, JDIMENSION * in_row_group_ctr,
       JDIMENSION in_row_groups_avail,
       JSAMPARRAY output_buf, JDIMENSION * out_row_ctr,
       JDIMENSION out_rows_avail ) );
#ifdef QUANT_2PASS_SUPPORTED
METHODDEF void post_process_prepass
JPP( ( j_decompress_ptr cinfo,
       JSAMPIMAGE input_buf, JDIMENSION * in_row_group_ctr,
       JDIMENSION in_row_groups_avail,
       JSAMPARRAY output_buf, JDIMENSION * out_row_ctr,
       JDIMENSION out_rows_avail ) );
METHODDEF void post_process_2pass
JPP( ( j_decompress_ptr cinfo,
       JSAMPIMAGE input_buf, JDIMENSION * in_row_group_ctr,
       JDIMENSION in_row_groups_avail,
       JSAMPARRAY output_buf, JDIMENSION * out_row_ctr,
       JDIMENSION out_rows_avail ) );
#endif


/*
 * Initialize for a processing pass.
 */

METHODDEF void
start_pass_dpost( j_decompress_ptr cinfo, J_BUF_MODE pass_mode ) {
    my_post_ptr post = (my_post_ptr) cinfo->post;

    switch ( pass_mode ) {
        case JBUF_PASS_THRU:
            if ( cinfo->quantize_colors ) {
                /* Single-pass processing with color quantization. */
                post->pub.post_process_data = post_process_1pass;
                /* We could be doing buffered-image output before starting a 2-pass
                 * color quantization; in that case, jinit_d_post_controller did not
                 * allocate a strip buffer.  Use the virtual-array buffer as workspace.
                 */
                if ( post->buffer == NULL ) {
                    post->buffer = ( *cinfo->mem->access_virt_sarray )
                                   ( (j_common_ptr) cinfo, post->whole_image,
                                    (JDIMENSION) 0, post->strip_height, TRUE );
                }
            } else {
                /* For single-pass processing without color quantization,
                 * I have no work to do; just call the upsampler directly.
                 */
                post->pub.post_process_data = cinfo->upsample->upsample;
            }
            break;
#ifdef QUANT_2PASS_SUPPORTED
        case JBUF_SAVE_AND_PASS:
            /* First pass of 2-pass quantization */
            if ( post->whole_image == NULL ) {
                ERREXIT( cinfo, JERR_BAD_BUFFER_MODE );
            }
            post->pub.post_process_data = post_process_prepass;
            break;
        case JBUF_CRANK_DEST:
            /* Second pass of 2-pass quantization */
            if ( post->whole_image == NULL ) {
                ERREXIT( cinfo, JERR_BAD_BUFFER_MODE );
            }
            post->pub.post_process_data = post_process_2pass;
            break;
#endif /* QUANT_2PASS_SUPPORTED */
        default:
            ERREXIT( cinfo, JERR_BAD_BUFFER_MODE );
            break;
    }
    post->starting_row = post->next_row = 0;
}


/*
 * Process some data in the one-pass (strip buffer) case.
 * This is used for color precision reduction as well as one-pass quantization.
 */

METHODDEF void
post_process_1pass( j_decompress_ptr cinfo,
                    JSAMPIMAGE input_buf, JDIMENSION * in_row_group_ctr,
                    JDIMENSION in_row_groups_avail,
                    JSAMPARRAY output_buf, JDIMENSION * out_row_ctr,
                    JDIMENSION out_rows_avail ) {
    my_post_ptr post = (my_post_ptr) cinfo->post;
    JDIMENSION num_rows, max_rows;

    /* Fill the buffer, but not more than what we can dump out in one go. */
    /* Note we rely on the upsampler to detect bottom of image. */
    max_rows = out_rows_avail - *out_row_ctr;
    if ( max_rows > post->strip_height ) {
        max_rows = post->strip_height;
    }
    num_rows = 0;
    ( *cinfo->upsample->upsample )( cinfo,
                                    input_buf, in_row_group_ctr, in_row_groups_avail,
                                    post->buffer, &num_rows, max_rows );
    /* Quantize and emit data. */
    ( *cinfo->cquantize->color_quantize )( cinfo,
                                           post->buffer, output_buf + *out_row_ctr, (int) num_rows );
    *out_row_ctr += num_rows;
}


#ifdef QUANT_2PASS_SUPPORTED

/*
 * Process some data in the first pass of 2-pass quantization.
 */

METHODDEF void
post_process_prepass( j_decompress_ptr cinfo,
                      JSAMPIMAGE input_buf, JDIMENSION * in_row_group_ctr,
                      JDIMENSION in_row_groups_avail,
                      JSAMPARRAY output_buf, JDIMENSION * out_row_ctr,
                      JDIMENSION out_rows_avail ) {
    my_post_ptr post = (my_post_ptr) cinfo->post;
    JDIMENSION old_next_row, num_rows;

    /* Reposition virtual buffer if at start of strip. */
    if ( post->next_row == 0 ) {
        post->buffer = ( *cinfo->mem->access_virt_sarray )
                       ( (j_common_ptr) cinfo, post->whole_image,
                        post->starting_row, post->strip_height, TRUE );
    }

    /* Upsample some data (up to a strip height's worth). */
    old_next_row = post->next_row;
    ( *cinfo->upsample->upsample )( cinfo,
                                    input_buf, in_row_group_ctr, in_row_groups_avail,
                                    post->buffer, &post->next_row, post->strip_height );

    /* Allow quantizer to scan new data.  No data is emitted, */
    /* but we advance out_row_ctr so outer loop can tell when we're done. */
    if ( post->next_row > old_next_row ) {
        num_rows = post->next_row - old_next_row;
        ( *cinfo->cquantize->color_quantize )( cinfo, post->buffer + old_next_row,
                                               (JSAMPARRAY) NULL, (int) num_rows );
        *out_row_ctr += num_rows;
    }

    /* Advance if we filled the strip. */
    if ( post->next_row >= post->strip_height ) {
        post->starting_row += post->strip_height;
        post->next_row = 0;
    }
}


/*
 * Process some data in the second pass of 2-pass quantization.
 */

METHODDEF void
post_process_2pass( j_decompress_ptr cinfo,
                    JSAMPIMAGE input_buf, JDIMENSION * in_row_group_ctr,
                    JDIMENSION in_row_groups_avail,
                    JSAMPARRAY output_buf, JDIMENSION * out_row_ctr,
                    JDIMENSION out_rows_avail ) {
    my_post_ptr post = (my_post_ptr) cinfo->post;
    JDIMENSION num_rows, max_rows;

    /* Reposition virtual buffer if at start of strip. */
    if ( post->next_row == 0 ) {
        post->buffer = ( *cinfo->mem->access_virt_sarray )
                       ( (j_common_ptr) cinfo, post->whole_image,
                        post->starting_row, post->strip_height, FALSE );
    }

    /* Determine number of rows to emit. */
    num_rows = post->strip_height - post->next_row;/* available in strip */
    max_rows = out_rows_avail - *out_row_ctr;/* available in output area */
    if ( num_rows > max_rows ) {
        num_rows = max_rows;
    }
    /* We have to check bottom of image here, can't depend on upsampler. */
    max_rows = cinfo->output_height - post->starting_row;
    if ( num_rows > max_rows ) {
        num_rows = max_rows;
    }

    /* Quantize and emit data. */
    ( *cinfo->cquantize->color_quantize )( cinfo,
                                           post->buffer + post->next_row, output_buf + *out_row_ctr,
                                           (int) num_rows );
    *out_row_ctr += num_rows;

    /* Advance if we filled the strip. */
    post->next_row += num_rows;
    if ( post->next_row >= post->strip_height ) {
        post->starting_row += post->strip_height;
        post->next_row = 0;
    }
}

#endif /* QUANT_2PASS_SUPPORTED */


/*
 * Initialize postprocessing controller.
 */

GLOBAL void
jinit_d_post_controller( j_decompress_ptr cinfo, boolean need_full_buffer ) {
    my_post_ptr post;

    post = (my_post_ptr)
           ( *cinfo->mem->alloc_small )( (j_common_ptr) cinfo, JPOOL_IMAGE,
                                        SIZEOF( my_post_controller ) );
    cinfo->post = (struct jpeg_d_post_controller *) post;
    post->pub.start_pass = start_pass_dpost;
    post->whole_image = NULL;/* flag for no virtual arrays */
    post->buffer = NULL;    /* flag for no strip buffer */

    /* Create the quantization buffer, if needed */
    if ( cinfo->quantize_colors ) {
        /* The buffer strip height is max_v_samp_factor, which is typically
         * an efficient number of rows for upsampling to return.
         * (In the presence of output rescaling, we might want to be smarter?)
         */
        post->strip_height = (JDIMENSION) cinfo->max_v_samp_factor;
        if ( need_full_buffer ) {
            /* Two-pass color quantization: need full-image storage. */
            /* We round up the number of rows to a multiple of the strip height. */
#ifdef QUANT_2PASS_SUPPORTED
            post->whole_image = ( *cinfo->mem->request_virt_sarray )
                                ( (j_common_ptr) cinfo, JPOOL_IMAGE, FALSE,
                                 cinfo->output_width * cinfo->out_color_components,
                                 (JDIMENSION) jround_up( (long) cinfo->output_height,
                                                        (long) post->strip_height ),
                                 post->strip_height );
#else
            ERREXIT( cinfo, JERR_BAD_BUFFER_MODE );
#endif /* QUANT_2PASS_SUPPORTED */
        } else {
            /* One-pass color quantization: just make a strip buffer. */
            post->buffer = ( *cinfo->mem->alloc_sarray )
                           ( (j_common_ptr) cinfo, JPOOL_IMAGE,
                            cinfo->output_width * cinfo->out_color_components,
                            post->strip_height );
        }
    }
}
